U.S. patent application number 10/745414 was filed with the patent office on 2004-07-15 for ultrasound assisted process for increasing the crystallinity of slow crystallizable polymers.
This patent application is currently assigned to The University of Akron. Invention is credited to Isayev, Avraam, Rieckert, Horst Hans.
Application Number | 20040138410 10/745414 |
Document ID | / |
Family ID | 32775599 |
Filed Date | 2004-07-15 |
United States Patent
Application |
20040138410 |
Kind Code |
A1 |
Isayev, Avraam ; et
al. |
July 15, 2004 |
Ultrasound assisted process for increasing the crystallinity of
slow crystallizable polymers
Abstract
In general, the present invention provides a process for
increasing the crystallinity of a slow crystallizable polymer. In
this process, at least one slow crystallizable polymer is
introduced to a pressurized treatment zone along a flow direction,
and is subjected, at the pressurized treatment zone, to
longitudinal vibrations of ultrasonic waves. In a particularly
preferred process, the ultrasonic waves propagate in a direction
perpendicular to the flow direction of the at least one slow
crystallizable polymer.
Inventors: |
Isayev, Avraam; (Akron,
OH) ; Rieckert, Horst Hans; (Calw, DE) |
Correspondence
Address: |
GeorgeW. Moxon II, Esq.
Roetzel & Andress
222 S. Main St.
Akron
OH
44308
US
|
Assignee: |
The University of Akron
|
Family ID: |
32775599 |
Appl. No.: |
10/745414 |
Filed: |
December 23, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10745414 |
Dec 23, 2003 |
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10342075 |
Jan 14, 2003 |
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6713600 |
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Current U.S.
Class: |
528/502R |
Current CPC
Class: |
C08G 69/08 20130101;
C08G 63/88 20130101; B01J 19/20 20130101; C08J 3/28 20130101; B01J
19/10 20130101; C08G 69/10 20130101; C08J 2367/02 20130101 |
Class at
Publication: |
528/502.00R |
International
Class: |
C08F 006/00 |
Claims
What is claimed is:
1. A crystallized polymer prepared by a process for increasing the
crystallinity of a crystallizable polymer comprising the steps of:
introducing at least one crystallizable polymer to a pressurized
treatment zone along a flow direction; subjecting the at least one
crystallizable polymer, at the pressurized treatment zone, to
ultrasonic waves.
2. The crystallized polymer prepared by the process of claim 1,
wherein the ultrasonic waves in said step of subjecting, propagate
in a direction perpendicular to the flow direction of the at least
one crystallizable polymer.
3. A process for increasing the crystallinity of a crystallizable
polymer comprising the steps of: introducing at least one
crystallizable polymer to a pressurized treatment zone along a flow
direction; subjecting the at least one crystallizable polymer, at
the pressurized treatment zone, to ultrasonic waves.
4. A process for making a polymer product of increased
crystallinity comprising the steps of: introducing at least one
crystallizable polymer to a pressurized treatment zone along a flow
direction; subjecting the at least one crystallizable polymer, at
the pressurized treatment zone, to ultrasonic waves; and thereafter
immediately shaping the at least one crystallizable polymer into a
desired product.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an ultrasound assisted
process for increasing the crystallinity and crystallization rate
of slow crystallizable polymers. More particularly, the present
invention relates to a process wherein slow crystallizable polymer
melts are subjected to ultrasound treatment, in a pressurized
treatment zone, to bring about an increased rate of
crystallization. Slow crystallizable polymers, such as polyesters,
are of particular interest.
[0002] The conversion of a crystallizable polymer from the
amorphous to crystalline state is generally achieved simply through
cooling of the crystallizable polymer. Increasing the rate of
crystallization or the level of crystallinity can also be achieved
by stretching of the crystallizable polymer, under certain
temperature conditions. This method, however, involves apparatus
for stretching and heating, and may only be used when producing
certain products, such as, for example, spun fibers or drawn
films.
[0003] There exist a need in the art for a process to increase the
crystallinity of a crystallizable polymer during other processes,
such as blow molding, injection molding, and extrusion. The process
of the present invention serves to provide a means for increasing
the crystallinity or rate of crystallization of crystallizable
polymers, particularly "slow" crystallizable polymers, in processes
not limited to those involving stretching and heating, and will
include processes such as blow molding, injection molding and
extrusion.
[0004] Herein, "slow crystallizable polymers" are to be considered
those crystallizable polymers that exhibit crystallization rates
lower than that of polyolefins, such as polyethylene and
polypropylenes. By way of non-limiting example, slow crystallizable
polymers include certain types of polyesters, polyimides and
polyethers. Given the criteria above, "slow crystallizable
polymers" will be readily identifiable by those of skill in the
art.
[0005] Polyesters are of particular interest in the present
invention. Polyesters are widely used to manufacture fibers, films,
bottles, and other various molded extruded, and spun products, and
are known to be slow crystallizable polymers. The ability to
control their crystallinity during processing methods, such as
molding, extrusion, and fiber spinning, would allow for the
manufacture of products having desirable properties. Thus, in a
particular embodiment, the present invention proposes an ultrasonic
assisted process for making novel polyester resins and products
thereof having controlled crystallinity.
SUMMARY OF THE INVENTION
[0006] In general, the present invention provides a process for
increasing the crystallinity of a slow crystallizable polymer. In
this process, at least one slow crystallizable polymer is
introduced to a pressurized treatment zone along a flow direction,
and is subjected, at the pressurized treatment zone, to
longitudinal vibrations of ultrasonic waves. In a particularly
preferred process, the ultrasonic waves propagate in a direction
perpendicular to the flow direction of the at least one slow
crystallizable polymer.
[0007] The process herein is practiced as a continuous process,
and, after ultrasonic treatment in the pressurized treatment zone,
the at least one slow crystallizable polymer may be advanced to
typical molding, extruding, fiber spinning or other apparatus.
Thus, the crystallinity of the at least one slow crystallizable
polymer may be controlled during processes for manufacturing useful
products from such polymers.
[0008] Without wishing to be bound to any particular theory, the
increased crystallinity of the slow crystallizable polymers
subjected to the present process is believed to be due to a
rearrangement and change of mobility of the crystallizable entities
in the at least one slow crystallizable polymer that is brought
about by the application of the ultrasonic waves. For a given
crystallizable polymer or mixture of multiple crystallizable
polymers, it may be possible to prepare polymer resins of
controlled crystallinity suitable to manufacture products having
desirable properties.
[0009] As a product of the present process, this invention provides
a crystallized polymer prepared by the process for increasing the
crystallinity of a crystallizable polymer comprising the steps of
introducing at least one slow crystallizable polymer to a
pressurized treatment zone and subjecting the at least one
crystallizable polymer, at the pressurized treatment zone, to
longitudinal vibrations of ultrasonic waves. These crystallizable
polymer products are preferably introduced to the pressurized zone
along a flow direction that is perpendicular to the direction in
which the ultrasonic waves propagate.
DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic of a cross-sectional view of a reactor
for practicing this invention, including a single screw extruder
having a die with two ultrasonic horns placed before the die and
perpendicular to the screw axis;
[0011] FIG. 2 is a schematic of a cross-sectional view of an
alternative reactor for practicing this invention, including a
single screw extruder with a dispersive distributive mixing section
and a die attachment into which the ultrasonic horns extend and are
separated by a gap.
PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION
[0012] It has been discovered that the application of certain
levels of ultrasonic amplitudes, in the presence of pressure and
heat, unexpectedly enhances the crystallization rate of slow
crystallizable polymers, such that products of increased
crystallinity can be achieved as compared to products of the same,
yet untreated, slow crystallizable polymer. The process of the
present invention generally entails feeding at least one slow
crystallizable polymer into a pressurized treatment zone, and
subjecting this at least one slow crystallizable polymer, while in
the molten state, to treatment with longitudinal vibrations of
ultrasonic waves, within this pressurized treatment zone.
[0013] In one embodiment, the process is carried out as a
continuous process, such that the at least one slow crystallizable
polymer flows into and through the pressurized treatment zone in a
particular flow direction, and is subjected to ultrasonic waves. In
preferred embodiments of this continuous process, the ultrasonic
waves propagate in a direction perpendicular to the flow direction
of the at least one slow crystallizable polymer. In either case, at
the exit of the pressurized treatment zone, the at least one slow
crystallizable polymer, which has just been subjected to ultrasonic
treatment, may be advanced to well-known apparatus for molding,
extrusion, or fiber spinning, or, indeed, may be advanced to any
other applications in which the treated slow crystallizable polymer
might be deemed useful.
[0014] Slow crystallizable polymers are generally known in the art,
and any such polymer may be employed to practice the present
invention. It will be appreciated that "slow crystallizable
polymer" is not easily defined, but, rather, is more or less
understood from qualified, rather than quantified, properties. For
purposes herein the term "slow crystallizable polymer(s)" is to be
understood to describe those polymers that are mainly amorphous in
the undeformed melt state, and can be obtained in an amorphous
state after rapid cooling, although they might crystallize upon
stretching or, annealing. Suitable slow crystallizable polymers for
use in this invention include, without limitation, slow
crystallizable polyesters, slow crystallizable wholly aromatic
polyesters, slow crystallizable copolyesters, slow crystallizable
polyamides, slow crystallizable polyethers and poly (phenylene
sulfide).
[0015] Crystallizable polyesters for use in the present invention
include, without limitation, polyethylene terephthalate (PET),
polybutylene terephthalate (PBT), polyethylene naphthalate (PEN),
poly(3-oxybutanoate), copolyesters and wholly aromatic polyesters.
Non-limiting examples of suitable slow crystallizable polyamides
include various polyamides (such as Nylons), poly(hexamethylene
adipamide), poly(m-phenylene isophthalamide), poly(metaxylylene
adipamide), and poly(ester esteramide). Suitable crystallizable
polyethers may include, without limitation, polyetheretherketone,
polyetherketone, and crystallizable substituted (e.g. halo)
polyolefins such as substituted polyvinylidenes. By further example
suitable slow crystallizable polymers include polyhydroxybutyric
acid, poly(vinylidene fluoride), polyoxymethylene and
polyoxyethylene.
[0016] The ultrasonic assisted process of this invention is
employed with "at least one" slow crystallizable polymer. Thus, it
will be appreciated that the polymer melt that is treated as herein
disclosed may include more than one slow crystallizable polymer or
may include additional, noncrystallizable polymers. The polyesters
are of particular concern. Thus, in particularly preferred
embodiments, the polymer melt that is ultrasonically treated
according to this invention includes a polyester selected from PET,
PBT, PEN, copolyesters, wholly aromatic polyesters, and mixtures
thereof.
[0017] In the continuous process embodiment, the pressurized
treatment zone is preferably provided by a continuous-flow
apparatus that can exert pressure on an at least one slow
crystallizable polymer melt and advance the polymer melt, after
ultrasonic treatment, to a desired product-forming apparatus or
shaping zone, such as, but not limited to, an extrusion apparatus,
blow molding apparatus, injection molding apparatus, film drawing
apparatus, or fiber spinning apparatus. Single and twin screw
extruders are particular, non-limiting examples of useful apparatus
of this kind. Even when only one slow crystallizable polymer,
without any additional components, comprises the at least one slow
crystallizable polymer melt to be treated, the mixing action of an
extruder will be found to be advantageous because the mixing motion
will help to bring a greater amount of the polymer melt into close
proximity to the ultrasonic horns employed. A dispersive or
distributive mixer might also be employed as a mixing zone
incorporated into the continuous-flow apparatus to achieve
beneficial and more uniform results. The mixing action is
particularly beneficial when the at least one slow crystallizable
polymer melt includes more than one slow crystallizable polymer or
a crystallizable polymer and additional components. Non-limiting
examples of useful continuous-flow apparatus include single screw
extruders, pin barrel extruders, twin screw extruders, single screw
extruders with attached static mixers, single screw extruders with
mixing sections, twin screw extruders with attached mixing
sections, Buss Ko-Kneader extruders, modular twin screw extruders,
and the like.
[0018] Referring now to the drawings, wherein the showings are for
purposes of illustrating the preferred embodiment of the invention
only and not for purposes of limiting the same, the Figures show
the application of ultrasonic treatment to the production of
polymers of increased crystallinity as compared to the same, yet
non-ultrasonically treated, polymers.
[0019] With reference to FIG. 1, a particular embodiment of a
continuous-flow apparatus for carrying out this invention is
generally represented by the numeral 10. Apparatus 10 includes a
single screw extruder 12, with two ultrasonic horns 14 placed
proximate the extruder exit 16, perpendicular to the screw axis. As
shown, single screw extruder 12 includes a barrel 18, which is fed
through hopper 20. Screw 22, within barrel 18, is capable of
advancing a polymer melt toward exit 16 in die 24. Thus, the at
least one slow crystallizable polymer may be added at hopper 20 and
advanced toward exit 16. Typically, the at least one slow
crystallizable polymer would be added as polymer pellets, and the
apparatus 10 would be maintained at a high enough temperature to
form a polymer melt of the polymer pellets fed thereto. Exit 16
will resist polymer flow and, therefore, it will be appreciated
that the at least one slow crystallizable polymer will be placed
under pressure inside barrel 18.
[0020] Thus, at least one slow crystallizable polymer is added at
hopper 20 and advanced, in the molten state, by screw 22, from
hopper 20 to exit 16. As the polymer mixture is forced through exit
16 pressure is built up within barrel 18, due to the narrowing of
the path through which the polymer melt must advance. Upon
operation of ultrasonic horns 14, the polymer melt is subjected to
ultrasonic treatment proximate exit 16, and, thus, for purposes of
this invention, it is to be generally understood that the at least
one slow crystallizable polymer melt is advanced through a
pressurized treatment zone and is subjected to treatment with an
ultrasonic wave within this pressurized treatment zone. From this
pressurized treatment zone, the treated at least one slow
crystallizable polymer melt may be advanced to known
product-forming apparatus or shaping apparatus, which are generally
designated by the numeral 30. It should be noted that to realize
the benefits of the present invention in a shaped product, the
polymer melt, after ultrasonic treatment must be advanced to the
shaping zone and shaped within a short amount of time, and, thus,
should not be solidified in the interim between ultrasonic
treatment and shaping. It is preferred that the shaping zone be in
line with the treatment zone, as shown in FIGS. 1 and 2. The
product-forming apparatus or shaping zone may include, without
limitation, blow molding apparatus, injection molding apparatus,
film drawing apparatus, fiber spinning apparatus, and the like.
[0021] When either more than one slow crystallizable polymer is to
be employed as the polymer melt or when a single slow
crystallizable polymer is to be mixed with an additional component,
it should be appreciated that, while it is possible to add the
individual polymers to the hopper 20 as separate, individual
components, the polymers to be treated may be premixed and
pelletized before addition to an ultrasonic apparatus according to
this invention. In such instances, the polymers may be premixed in
an extruder, absent any ultrasonic treatment, cooled, and
thereafter pelletized, such that non-treated, pelletized polymer
mixtures may be fed to the apparatus wherein the mixture is to be
ultrasonically treated.
[0022] Pressure affects the process of the present invention by
introducing volumetric compression in the at least one slow
crystallizable polymer melt, leading to more efficient propagation
of the ultrasonic waves. Thus, an increase in pressure exerted on
the polymer melt during ultrasonic treatment will tend to increase
the effect of the ultrasonic waves, while a decrease in the
pressure exerted on the polymer melt during ultrasonic treatment
will tend to decrease the effect of the ultrasonic waves. In a
preferred embodiment of this invention, the pressure at the
treatment zone is between about 0.6 to about 35 MPa, but lower and
larger pressures are also envisioned.
[0023] While FIG. 1 and the discussion thereof has focused, in
particular, on the application of an extruder to advance the at
least one slow crystallizable polymer to a pressurized treatment
zone, there is no reason to limit the invention to such. Indeed, it
is merely necessary that the apparatus employed be capable of
advancing the at least one slow crystallizable polymer, in the
molten state, and under pressure, toward an ultrasonic treatment
zone wherein the at least one crystallizable polymer is exposed to
longitudinal ultrasonic waves.
[0024] As mentioned, the at least one slow crystallizable polymer
is to be ultrasonically treated while in the molten state.
Therefore, the apparatus employed should be capable of being
heated. The heating of the apparatus, such as with apparatus 10 of
FIG. 1, tends to decrease the internal pressure and leads to
reduction of the power consumption of the motor. When necessary,
heat may be added to the system to properly carry out this
invention. More particularly, the process of this invention is
carried out at a temperature that is above the melting point of the
individual polymers that make up the at least one slow
crystallizable polymer. Various polymer mixtures will require
processes carried out at various temperatures, and operable
temperatures may need to be determined experimentally for a given
at least one slow crystallizable polymer.
[0025] The energy imparted by the ultrasonic waves and imposed on
the at least one slow crystallizable polymer, in the presence of
pressure and heat, is believed to be responsible for increasing the
crystallization rate of the at least slow crystallizable polymer
and, thus, believed responsible for yielding polymer resins or
polymeric products of higher crystallinity as compared to products
of the same slow crystallizable polymers without ultrasonic
treatment.
[0026] Considerable latitude is permissible in selecting the wave
frequency and amplitude of the ultrasonic treatment, and, optimum
conditions for particular at least one crystallizable polymer melts
are best determined by experimental trials conducted on the
crystallizable polymer melt of interest. It has been found,
however, that the frequency of the waves should be in the
ultrasound region, i.e., at least 15 kHz, while the amplitude of
the waves can be varied from about one micron to about one hundred
microns, with the exact amplitude and frequency best suited for a
particular application being readily determined by experimentation
and crystallization levels achieved. For polyester melts, as seen
below in the Experimental Section, amplitudes of 5 .mu.m and 7.51
.mu.m were found to be particularly preferred.
[0027] It should be appreciated that, while the positioning of
ultrasonic horns 14, in the apparatus of FIG. 1, serves to disclose
a process in which the ultrasonic waves propagate in a direction
perpendicular to the flow direction of the at least one slow
crystallizable polymer, the present invention is not limited
thereto or thereby. Thus, the process of the present invention also
includes processes in which the ultrasonic waves propagate in
directions off of perpendicular to the direction of flow of the at
least one slow crystallizable polymer. Ultrasonic waves propagating
in a direction perpendicular to the flow direction are, however,
employed in the Experimental Section herein below, and are
particularly preferred.
[0028] Referring to FIG. 2, another embodiment of a continuous-flow
apparatus is depicted. Therein, a single screw extruder is also
employed, as with the embodiment of FIG. 1, and, in order to
facilitate disclosure, like parts of the apparatus of FIG. 2 have
received like numerals in comparison with FIG. 1, although
increased by 100. Thus, at least one slow crystallizable polymer is
added at hopper 120 and advanced, in the molten state, by screw
122, from hopper 122 exit 116. Exit 116, however, does not feed
directly to a product-forming or shaping zone, as with the
embodiment of FIG. 1. Rather, exit 116 feeds into a die attachment
124. Furthermore, ultrasonic horns 114 are not placed on the screw
side of exit 116, as they are in FIG. 1, but, rather, are
positioned in die attachment 124. In this configuration, the
ultrasonic horns 114 are placed in closer proximity, without the
bulk of extruder screw 122 placed therebetween. This configuration
is believed to be advantageous because of the possibility of
interaction of two ultrasonic waves emanating from two horns. The
ultrasonic horns 114 are configured with a gap 140 therebetween,
which may be determined according to the achievement of desired
experimental results, and which generally may range from about 0.5
mm to about 20 mm, with the understanding that the size of gap 140
might affect the crystallization rate. Generally, smaller gap sizes
are preferred, on the order of from about 0.5 mm to about 10 mm.
Gap sizes in the range of from 0.5 to 5 mm may also be
preferred.
[0029] FIG. 2 also shows an apparatus in which a dispersive or
distributive mixer, generally designated by the numeral 126, is
provided in barrel 118. As mentioned, such mixers 126 would be
particularly useful when employing more than one slow
crystallizable polymer or a mixture of one slow crystallizable
polymer with an additional component. The mixer 126 is, however,
optional. As with the embodiment of FIG. 1, the apparatus of FIG. 2
advances the polymer melt, after ultrasonic treatment, to a desired
product-forming apparatus or shaping zone 130. Parameters regarding
pressure, temperature, horn positioning, and wave frequency in
amplitude may vary as discussed above.
Experimental
[0030] In order to demonstrate the practice of the present
invention, the following examples have been prepared and tested as
described. The examples should not, however, be viewed as limiting
the scope of the invention. The claims will serve to define the
invention.
[0031] Bottle grade PET pellets were vacuum dried at 80.degree. C.
and then extruded using a single screw extruder. The single screw
extruder had a slit die attachment followed by a die having three
holes of 3.125 mm in diameter. The PET was fed at a rate of 5
lb/hr. The screw speed was set at 100 rpm, and the single screw
extruder had zone temperatures of 220C/240C/260C/260C/260C/260C.
The extrudates exiting the shaping die were cooled in a water bath
and drawn on to a take up bobbin that rotated at a constant speed.
Two 3.3 Kw ultrasonic power supplies, ultrasonic transducers,
booster, and water-cooled horns of square cross-sections of 38.1 by
38.1 mm.sup.2 imposed ultrasonic waves with a frequency of 20 KHz
and various amplitudes (5 and 7.5 .mu.m) on the PET melt. The horns
were placed in the slit die of rectangular cross-section, with
dimensions of 157.5.times.38.1.times.2 mm.sup.3. A pressure
transducer was placed in the slit die, before the treatment zone.
Extrusion runs were made with and without the imposition of
ultrasonic waves.
[0032] A summary of the extrusion conditions are provided
below.
1 Extrusion Conditions Under Ultrasonic Treatment Sample PET,
bottle grade Attached die 1/8" Diameter Distance from die exit to
water bath 6" Horn to Horn Gap Size (mm) 2 Screw speed (rpm) 100
Feed rate 5 lb/hr Rotational speed setting at take up 10
[0033]
2 Pressure at the die entrance Amplitude (.mu.m) Before treatment
zone (psi) 7.5 45-105 5 55-155 0 3500-4000
[0034] As shown by the data below in Table 1, it was discovered
that the untreated and treated PET samples unexpectedly showed
substantially different crystallization behavior. More
particularly, the treated and untreated samples were subjected to a
heating scan from room temperature to 300.degree. C., increasing at
10.degree. C. per minute, and conducted in a nitrogen atmosphere.
The samples not subjected to ultrasound showed a glass transition
temperature (Tg) of 72.1.degree. C., followed by cold
cyrstallization (Tc) at 137.5.degree. C., exhibiting a heat of
crystallization (A Hc) of 24.6 J/g, followed by a melting point
(T.sub.m) at 249.degree. C., with a heat of melting (.DELTA.
H.sub.m) of 41.3 J/g. The sample subjected to ultrasound at an
amplitude of 5 microns showed an elevated T.sub.g of 79.1.degree.
C., followed by melting, without cold crystallization, at T.sub.m
of 247.2.degree. C., with a (.DELTA. H.sub.m) of 38.7 J/g. The
sample subjected to ultrasound at 7.5 microns showed an elevated
T.sub.g of 89.2.degree. C., followed by melting, without cold
crystallization, at T.sub.m of 247.3.degree. C., with a (.DELTA.
H.sub.m) of 40.0 J/g.
[0035] Crystallinity was calculated for each of these samples by
dividing the difference between the heat of melting and heat of
crystallization by the heat of fusion of PET crystals (about 120
J/g). From this calculation, it is clear that the treated melt,
during cooling immediately after ultrasonic treatment, exhibited
unexpectedly much higher crystallization rate, leading to high
crystallinity upon cooling. This higher crystallinity level will be
present in products made of ultrasonically treated melts. However,
the effect disappears upon cooling and second heating scan, as
indicated in Tables 2 and 3.
3TABLE 1 Thermal characterization during first heating scan
PERKIN-ELMER DSC Sample: PET, bottle grade Ramp: 10 C/min; N.sub.2
gas purge 75 ml/mm Scan from room temperature to 300.degree. C.
Amplitude (.mu.m) T.sub.g(C.) T.sub.c(C.) .DELTA.Hc (J/g) T.sub.m
(C.) .DELTA.H.sub.m (J/g) 0 72.1 137.5 24.6 249.0 41.3 5 79.1 -- --
247.2 38.7 7.5 89.2 -- -- 247.3 40.0
[0036]
4TABLE 2 Thermal characterization during cooling scan PERKIN-ELMER
DSC Sample: PET, bottle grade Ramp: 10 C/min; N.sub.2 gas purge 75
ml/min Cooling from 300.degree. C. to room temperature after
1.sup.st heating scan Amplitude (.mu.m) T.sub.c(C.) .DELTA.Hc (J/g)
0 179.9 35.1 5 182.2 32.4 7.5 183.5 34.7
[0037]
5TABLE 3 Thermal characterization during second heating scan
PERKIN-ELMER DSC Sample: PET, bottle grade Ramp: 10 C/min; N.sub.2
gas purge 75 ml/min After cooling scan from room temperature to
300.degree. C. Amplitude (.mu.m) T.sub.g(C.) T.sub.m (C.) .DELTA.Hc
(J/g) 0 78.2 246.7 34.9 5 80.8 244.6 32.2 7.5 79.8 245.2 31.6
[0038] In light of the foregoing, it should thus be evident that
the process of the present invention, providing an ultrasound
assisted process for increasing the crystallinity of crystallizable
polymers, substantially improves the art. While, in accordance with
the patent statutes, only the preferred embodiments of the present
invention have been described in detail hereinabove, the present
invention is not to be limited thereto or thereby. Rather, the
scope of the invention shall include all modifications and
variations that fall within the scope of the attached claims.
* * * * *